Switch device including damping means

ABSTRACT

A SWITCH DEVICE FOR RELATIVELY HIGH-CAPACITY ELECTRICAL CIRCUITS. THE SWITCH DEVICE ELIMINATES CERTAIN UNDESIRABLE CHARACTERISTICS OF THE SWITCHING OPERATION BY DAMPING THE CONTACT OF THE CLOSING MEMBERS.

United States Patent [72] Inventors Wolfgang Koennecke Bad Hombura. vor der lllohe;

Gerhard Schleilenbaum, Hun/en weldmau, :1 mm W [2!] Appl. No. 804,156

[22] Filed Mar. 4, I969 [45] Patented June 28, 1971i [73] Assignee Hand! 81 Weber G.m.h.ll.

HuttentalGeim/eid, Germany [32] Priority Mar. 7, 11968 1 G a y [54] SWITCH DEVlCE INCLUDING DAMPWG MEANS 6 Claims,4 Drawing Figs.

[52] USJCIL 200/1166 15]] Int. Ct. v. liwllh 11/50 s0 rte/lawman ..2oo/34,166 (11 335/6l,62, 193

[56] ReierencesCited UNITED STATES PATENTS l,748,2l9 2/1930 116661 .0 200/166(H) 2,727,114 12/1955 KSS8lring.. 200/166 11 2,782,287 2/1957 Smith ..,200/166 1-1 ux 3,180,960 4/1965 Barkanetal.... 200/166(H) 3,214,559 10/1965 KesselringetaL. 200/166(H) Primary Examiner-H. 0. Jones Attorney-Norman S. Blodgett ABSTRACT: A switch device for relatively high-capacity electrical circuits. The switch device eliminates certain undesirable characteristics of the switching operation by damping the contact of the closing members.

PATENTED JUN28|971 3, 586 A12 INVENTORS WOLFGANG KOENNECME SWllTtIll-ll DEVICE INCLUDING DAMIPING MEANS BACKGROUND OF THE INVENTION On switching apparatus, especially those of medium and large capacities, the closing of the contacts is made at high speed. The pressure of the contacts is closed state takes place under relatively large spring forces. Such spring forces achieve, on one hand, a fast and secure closing of the contacts and, on the other hand, a high contact pressure; consequently, it achieves small transfer resistance in the closed state. During interruption of the contacts for opening of the switches, high acceleration is required to reduce burning of the contacts by small electric arcs. The mechanism for moving the movable contact, therefore, in general, is equipped with strong springs.

The closing of the contacts, by application of such large forces, is basically an advantage because creeping contact ac tion is surely prevented. However, it is of disadvantage in that the hard impact activated by large forces on the contact during closing creates recoil effects, which could cause bouncing in the contact areas and, therefore, causes a considerable burning of the contacts with high electric currents by switchon under high loads. Furthermore, it has been proven that the hard impact forces created by closing of the contacts require special expensive designs for the housing carrying the contact element and its mounting. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a switch device in which chattering on engagement is reduced.

Another object of this invention is the provision of a switch device in which burning of the contact areas is substantially eliminated.

A further object of the present invention is the provision of a switch device giving the benefits of high contact forces, but allowing the mounting of the elements in relatively simple and inexpensive housings.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

SUMMARY OF THE INVENTION In general, the present invention directs itself to the task of reducing the burning of switch contacts by closing of the contacts; this is achieved by arranging damping devices parallel to the springs, which give impact to the movable contact. The recoil effect is dampened or completely eliminated, which, otherwise, is present with common contact devices. In addi tion, the stationarycontacts are mounted elastically. It is of advantage to provide the stationary contact with a damping device. These damping devices are designed as a throttling passage of small diameter within a fluid cylinder. It has proven beneficial to use damping devices having friction areas working against each other under tension. A cylinder is used consisting of material with a high friction coefficient surrounded by a hollow cylinder which, for achieving elastic friction, is slotted longitudinally along the surface and is provided with a resilient ring surrounding its free end for providing elasticity. In a preferred design example, a hollow cylinder is used formed of material with a high friction coefficient which surrounds a cylindrical bolt. Hollow cylindrical halves are pressed radially against the cylindrical bolt by surrounding springs, so that a constant friction lock of long duration is secured and also automatic adjustment for wear. An especially simple design results in the use of a hollow member having a conical outside shape on which surrounding support members which are in tension are in the axial direction. Preferably, there are used a pressure spring consisting of conically-wound coils where the spring is used as support area and, at the same time, the remainder ofthe coil guarantees the tension.

It has also proven to be of value to use leaf springs as support springs for the contacts. In this arrangement, the contact holder for the movable contact can be designed preferably as cantilevered leaf springs in layers. It is beneficial in the use of leaf springs to equip at least the support area for the spring with a roughed surface.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a sectional view of s switch device embodying the principles of the present invention,

FIG. 2 is a sectional view of a modified form of the invention,

FIG. 3 is a sectional view of another version of the invention, and

FIG. 4 shows a further modification of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. II, which best shows the general features of the invention, a contact arm 1 of a circuit breaker is shown as carrying a movable contact element 3 on a carrier 2 having the shape of an angle. This movable contact element 3 is equipped at its underside with a contact piece d. The contact arm stretches through the opening 5 of the carrier 2. The opening in its upper area is slot-shaped and has a narrow area 6 surrounding the contact arm 1 nd is adjustable in height. The opening 5 on its base is broadened to permit the withdrawal of the carrier from the contact arm. The movable contact element 3 is maintained in tension by the spring 7. The spring supports itself with its upper end on a spring disc 8 which, with its collar, surrounds a cylinder 9 made from a material with high friction coefficient, such as is commonly used for brake and clutch linings. The lower end of the spring is supported on a collar of hollow cylinder 10, which, in turn, is fixedly mounted by use of a rivet head keeping the. connection between the carrier 2 and movable contact element 3. The in side diameter of the hollow cylinder 10 is adjusted to the outside diameter of cylinder 9 insuch a way that it surrounds cylinder 9 by a friction lock under sutfficient tension. To permit the fabrication within extended tolerances and maintain the friction block under usage, the hollow cylinder 10 is designed elastically; this is achieved by providing slots 11 along the surface line. For increase of the friction blockage and for the support of the elasticity, a spring ring 12 is inserted into a groove surrounding the hollow cylinder. The stationary contact element 13 is connected with a terminal 14' and supported by a spring 15, so that the contact element 13 is still somewhat swingable. Underneath the contact part 16 of the stationary contact element 13 is a groove 18 which is worked into the housing 17. A spring leaf 20 is embedded in the groove and keeps the stationary contact element in tension by means of the screw 19.

By closing of the contact elements and by the action of strong springs acting on the contact arm 1, the movable contact element 3 is accelerated in the direction of contact element 13. In the phase of touching of contact part 4 and 16, a motion impulse will be carried over, which would have a recoil effect on the movable contact part if contact 13 was supported rigidly. By the elastic support of the stationary contact 13 by leaf springs, according to this invention, the contact 13 will first retract a small distance and, during action of further movement of the contact arm, the movable contact will additionally follow up. The actual impact of the contact parts is, therefore, already reduced. The tendency to impact vibration is completely eliminated. By further action of the spring 7 through the contact arm, the cylinder 9 is driven into the hollow cylinder 10 and a friction force is induced along with the action of spring 7. The pressure of the contact parts will be increased by this action. The tendency for bouncing, as consequence of the motion impulse, which could lead to vibrations by the spring 7, is eliminated. This is because the friction force created by the dampings device consisting of the cylinder 9 and the surrounding hollow cylinder 10 acts against the tendency of lift-off of the movable contacts 3. Should there be vibrations in individual cases, then they are considerably reduced because the damping devices removes energy in a manner different from the common pressure springs in which momentum is stored within the vibration system.

A similar action is produced by the leaf spring 20. The leaf spring does not only take in mass forces within the first moment of contact and permit a small retraction of the contact part 16 of the stationary contact element 13, but the leaf spring is shaped in such a way that its free ends, the ends positioned on the underneath of stationary contact 13, are bent and displaced and, therefore, draw energy form the system by friction.

An increase in energy drawoff can be done by roughing the areas of support and keep them rough during operation by selection of corresponding material. It was proven to be of ad vantage to select for the leaf spring 20 a material which, by displacement under pressure beneath the stationary contact element 13, grips the material during energy consumption and will create irregularities on the surface.

During repressing, after the first contact phase, the damping device increases the pressure and makes it difficult to release the contact pieces from each other or may take the release impossible. Eventually, during still present bouncing waves, energy is drawn off from the system and the number of rebouncings is-reduced at least to one. The additional absorption and damping of the stationary contact element permits interception of the sudden stress within the small spring deflection activated by the impact of the movable contact by its mass inertia. Therefore, the forces released during impact are considerably reduced and necessary requirements for strength in the mounting devices for the stationary contact elements 13, i.e., the housing supporting the contact, can be considerably reduced. The central arrangement of the damping devices and springs assure that both act equiaxially and are positioned symmetrically to the contact pieces 4,16.

A modification of the invention, also using friction surface and a damping device for the movable contact element 3 can be seen in FIG. 2. A support piece 21 is riveted in a recess arranged on the upper side of the movable contact element 3, which surrounds, with its inside collar, a bolt 22 designed with an enlarged shoulder on its lower end. On the bolt is arranged a friction cylinder 23 supported and adjustable lengthwise by means of the threaded upper section of the bolt. The friction cylinder extends through the opening in the contact arm 1 and overlaps and limits the stroke of contact piece 3 which is maintained in tension by the spring 7. The friction cylinder is surrounded by two half shells 25 of friction material and encloses the cylinder by means of small slots in the direction parallel to the axis. The half shells 25 have conical outside surfaces 26 on which rest the coils of the spring 7 which expand towards the end. The spring 7 brings the half shells 25 into tension in the axial direction against the support arm 1 and has a tendency to push the half shells so far to the top that not only the spring rests on the support arm, but the support arm also rests on the upper collar of the friction cylinder 23. By shifting friction cylinder 23 along its threads, the desired stroke may be adjusted and its position fixed by tightening the counter screw 24. On the basis of the conical-shaped half shells 25 and by the action of the axially-directed tension, a radial directed force acts on the surface of friction cylinder 23 which presses the friction halfshells tightly with constant force during operation against the friction cylinder 23. The design of the lower bolt 22 with its collar assures a certain swingability of the movable contact 3 around a small angle, so that, by support of the contact parts, it may adjust itself to the large support area. The design shown in FIG. 2 achieves a constant damping over a long period of time with a small number of parts. It also makes possible the support of the movable contact element 3 on the arm 1 by the adjusting means.

ln FIG. 3 another clamping device is shown using a hydraulic cylinder 28 with a closing cover 27. A piston rod 29 is sealed by a packing 30 and guided by the cover connected with a spring disc 8. Because of its simple design, no throttle hole or fluid canals are shown. The tolerances of the piston are selected in such a way that by operating with a pressure fluid, the desired damping effect is achieved. Also, the friction occurring by use of the packing 30 is very light, but this increases the action of the damping device, anyway.

A further variation of the invention is shown in FIG. 4. The insulated square shaft 31 connected with the switch lock of a circuit breaker transfers the movements to the contact arms of the contact pairs arranged for the individual terminals and is locked together by a clamp which is connected to a number of leaf springs. A support 34 fitted to the leaf springs is attached to the movable contact element 3. At the place of clamping, the individual leaf springs are separated by spacers 35 to achieve a large base for the triangular spring bundle formed by the leaf springs. The leaf springs are shaped in such a way that their free ends, by supporting each other, achieve large areas of support against each other. The leaf springs are made of equal length so that they may be surrounded by the support 34. A special spring of the type shown in FIGS. 1 to 3 is not necessary in this design, and the leaf springs exert friction forces on one another during stress because of length displacement by bending and act as a damping device. The whole spring package is substituted for the contact arm, spring, and damping device at the same time. To achieve high contact pressures, the spring package is maintained in tension in its base position against a support arm 36 connected to the clamp 32.

By inclusion of damping devices in accordance with this invention, the activated placing of contacts to contact devices on electrical switch devices, the bouncing during impact is suppressed or extensively reduced. Contact burning is practically eliminated. The action of the damping device is increased by mounting the second contact springs where a damping device works parallel to the spring. By the use of this invention, the life of the contact elements may be improved considerably.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. it is not, however, desired to confine the invention to the exact form herein shown and described, but is is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

We claim:

l. A switch device, comprising:

a. a stationary contact element,

b. a movable contact element,

c. spring means maintaining the contact elements normally in operative engagement, and

d. a damping device operatively arranged with the spring means and including a first cylinder whose outer surface is of high friction coefficient, a second hollow cylinder surrounding said first cylinder, said second cylinder being slotted lengthwise, and a ring which surrounds and constricts the free end of the second cylinder.

2. A switch device as recited in claim 1, wherein the ring is a garter spring.

3. A switch device, comprising:

a. a stationary contact element,

b. a movable contact element,

c. a spring means maintaining the contact elements normally in operative engagement, and

d. a damping means operatively arranged with the spring means and including a hollow cylinder formed of half shells of a material with a high friction coefficient and a cylindrical bolt surrounded by said hollow cylinder.

4. A switch device as recited in claim 3, wherein the hollow cylinder is pressed by a surrounding spring against the cylindrical bolt.

6. A switch device as recited in claim 5, wherein the resilient members are coils of a spring surrounding the conical outside surface and are in an axial tension. 

